27 Single center inception cohort of enthesitis-related arthritis: spectrum of characteristics, course and treatment approaches

Abstract Background Enthesitis-related arthritis (ERA) accounts for ∼10% to 20% of juvenile idiopathic arthritis (JIA) cases. Application of adult data to children with ERA is not ideal as less severe spinal involvement and more pronounced enthesitis and peripheral arthritis are present in children. Therefore, it is very important to conduct research that focuses specifically on the ERA population. Objectives This study aimed to present an ERA inception cohort and determine which entheses and joints are most commonly affected, course of the disease and treatment approaches. Methods Medical records of 546 patients with JIA who met each of the International League of Associations for Rheumatology (ILAR) criteria were evaluated retrospectively. An inception cohort of children with ERA who were diagnosed at Istanbul Faculty of Medicine between December 2020 and April 2022 was included. Patient characteristics were summarized by median and interquartile range (IQR) for continuous variables and frequency and percentage for categorical variables. P values <0.05 were considered statistically significant. All analyses were performed using SPSS statistical software version 28. Results There were 34 newly diagnosed ERA patients. Sixty percent were male, and the median age at the onset of the disease was 11.5 years (interquartile range [IQR] 9–14.8 years). The majority of the group met the ILAR criteria for a diagnosis of ERA at the first pediatric rheumatology visit (n = 29 [85.2%]), with 5 subjects (14.7%) meeting the criteria at the second visit. Twenty-three (69 %) subjects had enthesitis and arthritis at the time of diagnosis. The median number of tender entheses at presentation was 2 (IQR 0–4), and 20 subjects (58%) had at least 1 tender enthesis. The most frequent enthesitis were located on the patellar ligament insertion at the inferior pole of the patella, the plantar fascial insertion at the calcaneus, the Achilles tendon insertion at the calcaneus, and the plantar fascial insertion at the metatarsal heads. Fifty-five (19)% of patients had symmetric enthesitis. The most commonly affected joints were the sacroiliacs, knees, and ankles. Medication use varied significantly across sites for children with peripheral arthritis (p< 0.001), but not for sacroiliitis or enthesitis only. Nonsteroidal anti-inflammatory drugs and disease-modifying antirheumatic drugs were the most commonly prescribed treatments, with anti-TNF agents primarily being initiation for sacroiliitis. HLA-B27 positivity was associated with male sex, higher active joint count, sacroiliitis, and higher disease activity at disease onset. The Juvenile Spondyloarthritis Disease Activity Index (JSpADA) was significantly higher in those who were HLA-B27-positive than in those who were HLA-B27-negative (p = 0.03). Those who were HLA-B27-positive were more likely to develop arthritis after the age of 6 years (p< 0.01). Conclusion Either the observed heterogeneity in clinical presentation may result from differences in patient populations or from differences in the way ILAR criteria are applied. Most children have a pauciarticular onset and lower extremity enthesitis is common when ERA diagnosed.


Background
Enthesitis-related arthritis (ERA) accounts for $10% to 20% of juvenile idiopathic arthritis (JIA) cases. Application of adult data to children with ERA is not ideal as less severe spinal involvement and more pronounced enthesitis and peripheral arthritis are present in children. Therefore, it is very important to conduct research that focuses specifically on the ERA population. Objectives This study aimed to present an ERA inception cohort and determine which entheses and joints are most commonly affected, course of the disease and treatment approaches. Methods Medical records of 546 patients with JIA who met each of the International League of Associations for Rheumatology (ILAR) criteria were evaluated retrospectively. An inception cohort of children with ERA who were diagnosed at Istanbul Faculty of Medicine between December 2020 and April 2022 was included. Patient characteristics were summarized by median and interquartile range (IQR) for continuous variables and frequency and percentage for categorical variables. P values <0.05 were considered statistically significant. All analyses were performed using SPSS statistical software version 28.

Results
There were 34 newly diagnosed ERA patients. Sixty percent were male, and the median age at the onset of the disease was 11.5 years (interquartile range [IQR] 9-14.8 years). The majority of the group met the ILAR criteria for a diagnosis of ERA at the first pediatric rheumatology visit (n ¼ 29 [85.2%]), with 5 subjects (14.7%) meeting the criteria at the second visit. Twenty-three (69 %) subjects had enthesitis and arthritis at the time of diagnosis. The median number of tender entheses at presentation was 2 (IQR 0-4), and 20 subjects (58%) had at least 1 tender enthesis. The most frequent enthesitis were located on the patellar ligament insertion at the inferior pole of the patella, the plantar fascial insertion at the calcaneus, the Achilles tendon insertion at the calcaneus, and the plantar fascial insertion at the metatarsal heads. Fifty-five (19)% of patients had symmetric enthesitis. The most commonly affected joints were the sacroiliacs, knees, and ankles. Medication use varied significantly across sites for children with peripheral arthritis (p< 0.001), but not for sacroiliitis or enthesitis only. Nonsteroidal anti-inflammatory drugs and disease-modifying antirheumatic drugs were the most commonly prescribed treatments, with anti-TNF agents primarily being initiation for sacroiliitis. HLA-B27 positivity was associated with male sex, higher active joint count, sacroiliitis, and higher disease activity at disease onset. The Juvenile Spondyloarthritis Disease Activity Index (JSpADA) was significantly higher in those who were HLA-B27-positive than in those who were HLA-B27-negative (p ¼ 0.03). Those who were HLA-B27-positive were more likely to develop arthritis after the age of 6 years (p< 0.01).

Conclusion
Either the observed heterogeneity in clinical presentation may result from differences in patient populations or from differences in the way ILAR criteria are applied. Most children have a pauciarticular onset and lower extremity enthesitis is common when ERA diagnosed.

Background
The osteoarticular manifestations are proven during hematological malignancies in children, they can be the revealing symptom of the disease, and they may simulate a full clinical picture of Juvenile Idiopathic Arthritis (JIA), especially if no blasts are found in blood smear. Some therapies are common to both diseases, which commonly delay diagnosis for a couple of months and worsens the prognosis of these malignancies. We report three observations of patients treated for JIA which turned out to be acute leukaemia.

Clinical caises
The first patient is a 7-year-old male followed in pediatric rheumatology consultation for a monoarticular onset JIA. Since the patient did not respond to indomethacin, a bone marrow examination (BME) was performed before corticosteroid therapy (CST), no blasts were found. The patient received 01 month of CST which led to the amendment of clinical and biological signs, however, joint pain and bicytopenia reappeared after we started CST reduction. Blood and blood marrow smear were performed, leading to the diagnosis of acute Blymphoblastic leukaemia. The second patient is a 4 years old male admitted for exploration of polyarthritis with cervical lymphadenopathy, the initial assessment allowed the diagnosis of JIA with polyarticular onset. Indomethacin is prescribed, without any improvement. Radiological assessment was performed, as well as a complete blood count (CBC) which found neutropenia with lymphopenia, and blasts were discovered in the second BME. The third patient is a 6-year-old female admitted for exploration of arthralgia and pathological fractures. Radiological signs in favor of leukaemia and normochromic aregenerative normocytic anaemia were revealed, allowing the diagnosis of ALL B to be made after several consultations in rheumatology. Discussion Joint damage during leukaemia, called leukaemic arthritis, is frequent, complicating 12% to65% of pediatric leukaemia, most often ALL. It is linked to specific damage by leukaemic infiltration of the synovium or less likely to a synovial reaction to adjacent periosteal or capsular infiltration. In JIA there are incomplete or atypical forms, the differential diagnoses to be sought are numerous and depend on age, personal and family anamnesis and clinical, biological, hematological and radiological signs. The dread of a haematological malignancy must constantly be sought and excluded before the use of CST, which is one of the therapeutic weapons in ALL, thus causing the blasts to disappear and delaying the diagnosis.

Conclusion
The diagnosis of JIA must be made with caution, raise the possibility of haematological malignancy in children in the absence of response to usual treatments, in the presence of systemic signs such as fever or a persistent biological syndrome or atypical radiological lesions, hence the correct analysis of the CBC and the blood and marrow smears is clearly important.
Abstract citation ID: keac496.025 29 JUVENILE IDIOPATHIC ARTHRITIS AND OSTEOGENESIS IMPERFECTA: AN EXCEPTIONAL ASSOCIATION Hannech Emna 1,2 , Boussaid Soumaya 1,2 , Rekik Sonia 1,2 , Jemmali Samia 1,2 , Rahmouni Safa 1,2 , Ajlani Houda 1 , Sehli Hela 1,2 and Elleuch Mohamed 1,2 1 Rheumatology Department, La Rabta Hospital, Tunis, Tunisia, 2 Faculty of Medicine of Tunis, University Tunis El Manar Background Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic disease of unknown aetiology in childhood and predominantly presents with peripheral arthritis. Osteogenesis imperfecta (OI) is an autosomal dominant inherited disease defined by bone fragility due to abnormal collagen synthesis. It affects the entire skeleton, predisposing the patient to fractures. We report an uncommon association between osteogenesis imperfecta and juvenile idiopathic arthritis. Case presentation A 15-year-old child presented to our rheumatology department with medical history of recurrent bone fractures due to low-energy trauma since the age of five years. The patient was born from a consanguineous marriage. He has been diagnosed with a polyarticular JIA since the age of eight years-old. The initial clinical presentation was a symmetric, cumulative, large and small joint polyarthritis. The rheumatoid factor was negative. No other autoantibodies were detected. The patient was treated initially with methotrexate which was inefficient. He developed joint deformities. Then, biologic therapy was associated with a good response. Clinical examination on entry showed severe joint deformities touching elbows, wrists and interphalangeal joints. Arms and thighs were curved and an unequal leg length was noted. There was no arthritis. The patient has bluish sclera. Neurological and dental examination was normal. There was no hearing loss. Laboratory findings showed a normal C-reactive protein. Calcium and phosphate serum levels were within normal ranges. On radiological investigations, radiographs showed excessive trabecular bone transparency, cortical bone E POSTERS ii11